my tkd instructor always said it was just a training tool to teach beginners how to use more hip and shoulder action in their punches. like, if you're pulling back one shoulder/arm it kinda automatically pushes the other forward. but he made it very clear that you don't do that actually motion in a real situation.

Chambering is an excellent tool for beginners, it teaches proper technique, along with balance. Chambers are an effective way of learning a rear elbow strike, and can be used to release a grasp or cause pain on a block.

Having said all of that, chambers should be avoided in sparring and in a real self-defense situation. At our school, we train with chambers for forms and one-step sparring. We also train to throw kicks and punches without chambers in our sparring classes, to help with the element of surprise. If you chamber in a real situation, you are telegraphing your intentions, and that can be a downfall.

Sincerely,

Knowing it is not enough, we must apply.
Willing is not enough, we must do.

Knowing it is not enough, we must apply.
Willing is not enough, we must do.

Never approach a Bull from the front, a Horse from the rear, or a Fool from any direction!